POS0408 DEFECTIVE AUTOPHAGY IS ASSOCIATED WITH CHONDROCYTE SENESCENCE AND JOINT DAMAGE
Authors: P. Lopez de Figueroa, J. Fafian-Labora, I. Lorenzo, V. Calamia, M. Lotz, C. Lopez-Otín, F. J. Blanco, B. Carames
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Aging is a main risk factor of many major human diseases, including Osteoarthritis (OA). Compromised autophagy, a hallmark of aging, is involved in joint aging and OA and its activation protects against joint damage and disease. However, targets underlying this defective mechanism are still unknown. <h3>Objectives</h3> <i>Here, we aimed to identify targets regulating autophagy</i> with potential clinical relevance in joint aging and OA. <h3>Methods</h3> We performed a quantitative proteomic analysis of defective autophagy by Atg5 knockdown in human OA chondrocytes by using iTRAQ (isobaric tags for relative and absolute quantitation) labeling coupled LC/MS/MS. Protein identification and quantification were performed using Protein Pilot Software v 4.0. Each MS/MS spectrum was searched in the Uniprot/Swissprot database for <i>Homo sapiens</i>. Human cartilage and chondrocytes from healthy, aging and OA subjects were employed to investigate the role of Lamin A/C in aging and disease by western blot, and inmunohistochemistry. To test the relevance of Lamin A/C accumulation in joint tissues, a mutant mice model of accelerated aging by genetic deletion of Zinc Metalloproteinase STE24 (<i>Zmpste24</i><sup>-/-</sup>) was employed. The functional consequences of Lamin A/C accumulation on macroautophagy, inflammation, and senescence were determined in human chondrocytes. To evaluate the therapeutic effect of regulating Lamin A/C in human chondrocytes, Lonafarnib, an FDA approved drug for Progeria Syndrome, acting as Lamin A/C accumulation inhibitor, was employed. <h3>Results</h3> 24 out of 487 proteins were significantly altered (p&lt;0.05) in response to defective autophagy. Cytoskeleton organization, collagen catabolism, oxidative stress, and aging pathways were affected. Interestingly, Lamin A/C, a nuclear envelope protein implicated in cell senescence and aging, was found upregulated under defective autophagy. Increased Lamin A/C expression was found in human chondrocytes with reduced macroautophagy. Furthermore, increased Lamin A/C expression is found in aging and OA human cartilage. Importantly, <i>Zmpste24</i> KO mice showed bone damage and intervertebral disc degeneration (IDD), suggesting that Lamin A/C accumulation associated to deficient autophagy is correlated with aging and OA phenotype. Human chondrocyte premature aging by genetic knockdown of <i>Zmpste24</i>, lead to Lamin A/C accumulation, accompanied by a reduction of macroautophagy by <i>MAP1LC3B</i> downregulation, increased inflammation, cartilage degradation and senescence represented by upregulation of <i>NFKB/RELA, MMP13, CDKN1A and CDKN1A</i> respectively. Remarkably, inhibition of Lamin A/C accumulation by Lonafarnib upregulates macroautophagy and protects against inflammation, cartilage degradation and chondrocyte senescence. <h3>Conclusion</h3> The results suggest that increased LMNA due to autophagy defects compromises chondrocyte homeostasis and joint integrity, potentially contributing to systemic maladaptation that occurs in aging. Therefore, targeting Lamin A/C might be a promising strategy to develop novel therapeutics for cartilage aging and OA. <h3>Reference</h3> [1]Caramés B, et al. Arthritis Rheum. 2010, 2015; 2. Caramés B, et al. Ann Rheum Dis. 2012 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.